zaevor2000

Thanks Hacker for the input.

I was facing the same tossing and turning as the OP when I decided to change my oil recently.

I was going to go with 20w50, but then decided to look into the tech section and pulled the pdf I attached.

Since no one had any more to say on the pdf, I decided to go with 15w40, which is what my mechanic suggested made more sense as well instead of the 20w50.

Still tossing and turning on the decision since there are protagonists in each corner (the 15w40 vs 20w50 crowd).

SeanR

Why the hell is this still a debate. Unless you live above the artic circle.

Motul 15w-50.
Mobil 1 15w-50
Brad Penn 20w-50. (quicker oil changes)
Amzoil if you feel the need to buck the trend and be a fan boi.

Basically do not use anything below a 15w-50 oil unless you are a dip****.

God, why do I log in here.

Fly911

I did my research, and today I bought 15 quarts of Valvoline VR1 20W50 with high ZDDP. $36.69 at O'Reilly Auto Parts per 5qt bottle.

SeanR

Change it every 3000 miles and you will be good.

I'll stick with every 10,000k with Motul and never have a worry.

Cheburator

Shell Racing 10W60
Castrol Edge 10W60
Mobil 1 Motorsport 10W60
Motul 10W60

They all cover cold starts, are also excellent with regards to fuel dilution and can take prolonged abuse at high rpm... Oil changes every 7000 miles or once every 2 years....


P.S. The beauty of 10W60 is that I run it in all my cars - yes - the 928s, the 944T, the GT3 and the M3. The only exception is the F15 50i bi-turbo V8 BMW X5 which calls for 0W40 and does like to drink it...

Petza914

Driven DT50 or GP-1
I use this in 2 928s, a 914, a 944 S2 and a wakeboat. Has produced better UOA results than anything else I've tried.

Here's the UOA history on my 84 Euro S with 150k miles that came to me with Shell Rotella installed so that's the oldest column and DT50 for the more recent ones. It's the Moly as an anti-friction component that's the key. I run Driven oils in everything I own - 7 Porsches, an Audi Q5, the boat, and a GMC pickup.

Another interesting tidbit here is that the first 2 samples had an OEM air filter in the car and the last one a K&N...and the silicon or dirt content actually went down.

linderpat

oil threads

84dizzy

+1 for Brad Penn 20w50

FredR

These oil threads- in 23 years on Rennlist I cannot recall seeing a thread about how a 928 engine went **** up because of the make or grade of oil it ran on. Read of a few GT cams being damaged allegedly due to low ZDDP in the oil but whether such was ever proven conclusively I have no idea.

SAE stds did not come about by accident- maybe that is why SAE compliant lubes actually work. Evwe Porsche advised their local agents to fill my partially rebuilt S4 motor with Mobil 1 0W 40- laasted all of 5monutes before I iinstructed them to get it out and fill with a 20W50!

hacker-pschorr

Some of us have, but I already know you're going to say there isn't conclusive enough evidence to support the claim, so why bother?

When an engine shows damage, I trust what an engine builder says over all the oil data you can find.

Petza914

The PO of my son's 944 S2 used this VR1 so I'm interested to see the next couple UOA reports since we switched the car over to the DT50 I use. In all the UOA reports I've had done on different cars, I've never had the Driven oil be worse than what was in the car when I bought it. Since a bunch of classic car owners rave about this VR1, I'm especially interested to see what the numbers look like.

I know a bunch of 928 guys also use Shell Rotella Dino oil and that stuff in my 79 928 that's supercharged was a major failure compared to the DT50. Here's the UOA report on that where it came to me with fresh Rotella in it that I ran for the same interval as the the DT50 for all the subsequent changes..The bearing wear was terrible by comparison.

jbrob007

I change 15W50 or 20W50 motor oil every 5,000 miles. If I changed it every 3,000 miles I’d be changing it every month ☹️

The good ole Owners Manual says to change the oil at 10K and the filter every 15K…. I think ole Hans & Franz were a bit optimistic about the life of their oil. Still, every 3,000 seems pretty often IF you don’t have a ton of blow by and your oil isn’t black as burnt coffee after driving around the block… once!

In another vein, who’s going to Sharks Discover Columbus in July? I guarantee we won’t be talking about oil all weekend! More like who makes the best bourbon, scotch & cigars… 😎😎😎

Petza914

I'll be drinking those... and talking about oil
LOL

hacker-pschorr

I was in the same boat back when all that data was being shared for the first time. It made so much sense, why not switch? I trust Doug's data that it worked for his car, no idea what conditions or driving gave him such great results and some of us the complete opposite.

At the end of the day, reality is the owners manual is still correct.


Sean's comment about 3,000 miles is because that VR1 is non-synthetic. Fully synthetic VR1 comes in a black bottle.

You bring up a good point that are often not addressed in these threads: Driving Style.

If you read the fine print of many owners manuals, the recommended service intervals are based on perfect driving conditions. That means a mild ambient temperature, perfectly flat roads, steady state down the highway. If that's all you drive, your engine has far lower needs for lubrication than someone who does nothing but stop and go traffic. Talk to any shop that works on a lot of late model cars, those having the most engine issues are the cars that are driven often for short trips.
Recently we saw a BMW SUV with 25,000 miles that suddenly died, won't turn over. Long story short there was so much condensation built up in the oil one of the camshafts rusted to the housing. I couldn't make this sh*t up if I tried. The owner drove to work, five says a week, 4 miles. That is an engine that should have been changing oil every 1,000 miles. No amount of additives or oil quality would have survived that one.

The vast majority of 928's are pleasure vehicles. We fire them up and actually drive them. Now how hard you drive them varies from person to person, but reality is, these cars are so underpowered for what this engine was designed to take, you're probably not coming close to any physical limit on the street. Our cars are not sitting in traffic a lot, making short trips etc.... they are being driven as designed.
We also have a massive oil sump capacity. 10 quarts???? My 6.0 liter Denali holds 6 quarts with an oil filter the size of a tuna can and will easily last 300,000 miles (the body will rust away by 225k).

TLDR - we over think this. The manual says use a 15/20w-50 for most nice weather driving and as for ZDDP, you want 1,000 - 1,100ppm or more, and the vast majority of oils in this weight class have that.

Darklands

I think Porsche of the 80ies in Germany knows perfectly how hard customers could and will drive these cars.
The 24 h of Nardo record drive show this also.

The second thought is oil technology, oils from 2020 are way more evolved than oils from the 80ies so the Intervalls from Porsche from the past should have safety margins yet.

What is bad for engines, short trips with lot of fuel in the oil, I don‘t drive my 928 like my VW Caddy, the 928 needs in our climate 10 miles till the oil is hot so it‘s not soccer mums car anymore but the middle and long distance driver.